A common problem at sea is that, unless properly restrained, an anchor tends to wobble and bounce against its mounting bracket when the vessel carrying the anchor is working against waves. This problem is universal, but is of particular concern where the anchor is mounted on a bow pulpit or roller on a small to medium sized boat. Wobbling of the anchor is not, however, the only difficulty.
At sea, the anchor normally remains shackled to its chain. The chain is led over the bow roller, if one is provided, across at least part of the deck, and is stowed in an anchor locker. Unless the chain is tensioned, however, not only will the anchor itself wobble, the chain will slide and beat against the deck and eventually damage it. Accordingly, a tensioning clamp for the anchor chain is commonly installed on deck near the anchor locker. By holding the anchor chain taut, not only is the chain prevented from damaging the deck, the anchor itself is secured firmly against its bracket or roller.
Prior art tensioning clamps typically include a anchor hook, which pivots relative to a lever arm. The hook is provided for grasping one link of the anchor chain. The lever arm is then retracted to pull the anchor hook and link aft. The forward extension of the anchor hook is commonly made adjustable by threading the shaft of the anchor hook, which may then be screwed into or out of a anchor hook pivot shaft mounted transverse the lever arm. In some prior art tensioners, the anchor hook includes a turnbuckle to allow adjustment.
Unless the lever arm of the anchor chain tensioner is locked, it is possible for the anchor chain to raise it and release the anchor chain tension. Consequently, most prior art tensioners provide a locking pin for the lever arm, which extends across and above the handle end of the lever arm and into side walls of a base bracket.
The use of a separate locking pin is a major disadvantage of prior art tensioners. First, if the pin is not captive, it may easily be lost overboard. Second, in order to secure the lever arm, the user must insert the end of the pin through at least one often tight hole while holding the lever arm down. Not only may pin insertion be difficult, it is also dangerous, since both the user's hands are not free to steady him on the pitching, wet deck.
Even if the lever arm is secured, the problem remains that the anchor hook itself may pivot relative to the tensioner deck mounting, and the anchor chain, although more taut, may still slap against the deck as the anchor hook pivots. This problem is particularly pronounced when the chain loads the tensioner at a high angle. The anchor hook, too, should therefore also be positively locked.
The most obvious prior art solution to the problem of locking the anchor hook has been to provide a second locking pin. Of course, this simply compounds the difficulty and danger of properly tensioning the chain.
The SLVI Anchor Tensioner/Lock manufactured by the Deep Seven Co. is a known prior art tensioner which provides double locking without using two pins. Instead, the captive pin used in this device locks both the lever arm and the anchor hook. The lever arm is locked in the conventional manner by inserting one straight end of the pin through holes in a base bracket. The remainder of the pin, however, forms a torsion pin, which extends above and across the hook, then downward, pressing the hook to one side to lessen its freedom to pivot.
The SLVI tensioner suffers, however, from two primary shortcomings. First, it still requires the user to insert a pin through a tight hole at sea. Second, the resilience of the captive torsion pin is not great enough to prevent the hook from pivoting during strong, high-angle loading. Furthermore, this prior art tensioner requires a separate U-bracket for adjustably securing the hook to the hook pivot shaft.
The object of the present invention is to provide an easily adjustable chain tensioner which enables locking and unlocking of both the lever arm and the chain hook in one rapid motion, which is more secure than prior art tensioners, which requires a minimum of parts, and which requires no separate locking pins.